Socioeconomic status (SES) of the family of origin is a fundamental indicator of multiple and diverse environmental exposures that might be implicated in chronic disease etiology and survival. Research indicates that men and women with lower SES during childhood have an increased risk of mortality, independent of their socioeconomic characteristics in adulthood. The most consistent link has been established between lower childhood SES and an elevated risk of cardiovascular mortality. In addition, men and women from lower-SES families of origin have elevated mortality from respiratory and digestive diseases, diabetes, smoking-related cancers, and stomach and liver cancers. Yet existing research is characterized by several limitations. In most studies, early-life SES was assessed with one measure, typically fathers' education or occupation, often retrospectively. Moreover, few studies have explicitly examined gender and race differences in the effect of early-life SES on mortality and in the life course pathways explaining this effect. Finally, the mediating mechanisms linking childhood SES and adult mortality remain unclear. An important task is to broaden the methodological arsenal of life course epidemiology by employing methods that are consistent with the theoretical emphasis on life course pathways. Using data from the Wisconsin Longitudinal Study and the Health and Retirement Study, I will apply Cox regression and structural equation modeling to examine the effect of early-life SES on all-cause, cardiovascular, and cancer morality in later life as well as gender and race differences in this effect. Further, I propose to explore socioeconomic characteristics, marital status, and health behaviors in adulthood as mediators of the associations between early-life SES and late-life mortality. Finally, I will analyze whether and how causal pathways linking early-life SES and later-life mortality differ by gender and race. The proposed study will provide new evidence of life course trajectories of social advantage and disadvantage and heterogeneity of these trajectories by gender and race/ethnicity. Moreover, the exploration of mechanisms linking early-life socioeconomic environment to all-cause and cause-specific mortality in later life will improve our understanding of life stages that may be potentially the most important for prevention efforts.